Coking of heavy hydrocarbonaceous residues



Jan. 25, 1955 w. J. MATTox 2,700,642

COKIN@ oF HEAVY HYDRocARBoNAcEoUs REsInuEs Filed May s, 1951 asheets-sheet 1 I o 2 g u1 u v J (D s@ G d O l D, d d Ln l -H ci T 3L; L0f' J l 23 o f1 l :o 4 o L0 Ln l el O 3 2 K l v d l 'I5 i il l q) 4J i Qm; m L 0J lLl l @l y 0 l o f QJ@ e' COKING OF HEAVY HYDROCARBONACEOUSREASIDUES Filed May 8, 1951 2 Sheets-Sheet 2 G ILAQLED IZODLJCTS Excess@ons Am: FLUE GAS 'llasmuum 2 FEED j TIzANsi-al LNE. (ZO burma?. @Hem-ELFHL-2 Jillian? mattox {Srzvenbor had# Clbborrze .expansion coetcient.

'carriers are usually highly adsorptive.

United States Patent@ COKING F HEAVY HYDROCARBONACEOUS RESIDUES .WilliamJ. Mattox, Baton Rouge, ard Oil DevelopmentCompany, .ware

La., assignor to Standa corporation of Dela- The present :inventionIrelates to a method of treating hydrocarbons. More particularly, theinvention pertains to a method of upgrading heavy hydrocarbon materials,such as topped or reduced crude, asphalt, pitch or similar heavyresidues to produce more valuable, lower boiling oils including gas oilssuitable as feed stock for catalytic cracking, gasoline, lunsaturatedand aromatic hydrocarbons suitable for use as chemicals or startingmaterials therefor, etc., as well as coke. Briey, the invention providesfor contacting the residuum feed at coking conditions with a mass oflinely divided .solids having a substantially higher thermal coeicientof expansion than the coke formed in the coking reaction and subjectingthese solids carrying coke deposited thereon to temperature changesconducive to a disintegration of the coke layer Vby,a change in `size ofthe supporting solids particle having the higher thermal .Heretofore,heavy residues of the type specified, particularly atmospheric or,vacuum crude distillation residues have been `subjected to coking atrelatively severe conditions for the production of motor.fuels, heat ing.oil and gas oils. The coke produced in Vthis reaction is more thansufficient to supply `by combustion the heat requirements of theprocess. On the otherhand, complications arise from excess coke depositson the walls of the coking zoneand in transfer linesrequ iring frequent.interruption for the purpose of `cleaning out the coke. To alleviatethese diiculties subdivided, inert, adsorbent solids such ascoke,.pumice, sand, or the like have been added to the residuum feed toserve as a carrier material forthe coke and asa scouring agentpreventing cokedeposition on the equipment walls. The coke deposited onthese solids may be burnt olf incyclic or continuous fashion toregenerate the solids and to supply-the heat required for coking.

While moving bedand-suspensoid type systems have been proposed forthistype of operation, the s/o-called iiuid solids technique offersgreatest advantages ,with respect to temperature control, heateconomy,ease and continuity of operation aswell as equipment dimensions. .Thistechnique involves the injection of the feed into a relatively `densehighly turbulent bed kof hot subdivided solids ranging in size fromabout 30 to about 400 mesh. Fluidization is accomplished by gases andvapors flowing kupwardly through the bedat a linear superficialvelocityofabout 0.3-3 ft. per second to give the bed the appearance of aboiling liquid. Volatile coking products are removed overhead whilecoke-carrying solids maybe withdrawn directly, from theuidizedbed,reheated in `aseparate Cokefburningzone.Operated at a temperature abovecoking temperature and `returned to the coking zone for heat supply.

.While this technique atfordsconsiderable thermal and proceduraladvantages over othersystems, its adaptation to commercial scaleoperation has been impeded by various diiculties. The solids used ascoke andheat The result 4is that valuable, volatile coking products areadsorbed by the solids and lost in the reheating zone by combustion.When non-adsorptive solids are used in a conventional manner the utilityof the'product vcoke as 'a fuel or 'for other purposes is considerablyreduced. Furthermore, since more coke is produced in the coking reactionthan is required for heat generation, ,coke accumulates on the solidsparticles to vincrease their size, necessitating continuous orintermittent grinding of the solids to maintain their uidizable size.The present inventionovercomes these diculties and affords various otheradvantages as will appear hereinafter.

It is, theerfore, the principal object of the present invention toprovide an improved process for coking hydrocarbonaceous residues in thepresence of subdivided solids serving as cokecarriers. Other and morespecific objects will appear from the following description of theinvention wherein reference will be made to the accompanying drawing inwhich Figure l is a semi-diagrammatical illustration of a system adaptedto carry out an embodiment of the invention; and

Figure 2 is a similar illustration of a system applying the process ofthe invention to a somewhat modified type of operation.

-In accordance with the present invention, heavy hydrocarbonaceousresidues are contacted at coking conditions with a dense, turbulentuidized mass of finely divided metallic carrier solids which have adensity and thermal coei'licient of expansion substantially higher thanthose of the coke vdeposited thereon. Coke deposited on these solids inthe course of the coking operation is removed by subjecting the cokedsolids to a temperature change of sulicient magnitude to break up thecoke layer as the result of the difference in contraction or expansionof the coke and the supporting solids. The broken coke separates fromthe solids particles in the form of a loose nely divided material whichmay be removed from the carrier solids to any desired extent byelutriation, centrifugal separation or similar means. If desired, thecarrier solids of the invention may be chosen to exert a catalyticeffect in the coking lreaction by promoting desulfurization orconversion into particularly desirable products, such as aromatics orother reactions, for example, iron and its alloys act as desulfurizationcatalysts while copper and its alloys have aromatization activity.

When operating in accordance with the invention, carry-over of volatilecoking `products into the coke-burning zone by adsorption on the carriersolids is practically eliminated'because of the low surface area of thecarrier solids involved. The original size of the carrier solids may beretained without a special grinding stage. Excess coke may be recoveredin pure form Iand in a state of subdivision increasing its utility aslamp black. as a powdered fuel and for various other purposes. Theremoval of the coke from the mass of carrier solids may be readily soYconducted as to leavevsuiicient coke admixed with, and/or adhering to,lthe carrier .solids forlthe pur.- pose of generating by coke combustionthe heatrequired by the coking reaction.

The thermal coefficient of expansion ofthe `carrier solids should be atleast twice, and preferably at least three times, that of the cokewithin the temperature range involved in the temperature change used forbreaking up the coke layers. .When using suchsolids, temperature changesof about 50-300 F. are suitable for lthe purposes of the invention.Frequently'such changes occur in the normal operation of continuouscoking operations involving solids circulation between coking andcoke-burning'zones. In other cases, 'temperature changes of thismagnitude maybe incorporated without seriously affecting 'the heatbalance of` the systems.

In illustration vofv the type of carrier solids useful for the purposesof the invention, a number of metals land alloys are listed belowtogether with their thermal expansion coeicientsat the temperatures ofdetermination, as compared withcarbon. H owever, thelinvention isnotlimited to the solids listed.

of thermalv expansion of carbon and [Increase in length/unit lengthl 0.]

The thermal expansion coeicient of metals generally increases withincreasing temperatures while that of carbon is littleaiected bytemperature variations. It will be seen, therefore, that all carriersolids listed above have coefiicients at least about three times that ofcarbon within the temperature range of, say, about 800-1300 F. normallyassociated with coking operations. Of these solids, copper or brass and20% Ni steel are generally preferred, the former because of theircatalytic effect favoring coke desulfurization and the formation ofhighly aromatic cokng products, the latter because of its combination ofhigh density with a high expansion coeicient.

Carrier solids of the above or similar type may be used in the form ofspheres, oval, rod-shaped or irregularly shaped particles having a sizeof about 50 microns to about 1A inch diameter, sizes of about 200-1000microns being preferred to permit fluidization at gas velocities ofabout l-S ft. per second in commercially practical reactors and tofacilitate separation from the broken up coke particles. In order toenhance coke disintegration in the separation phase, the latteris-preferably carried out with the solids in a highly turbulentfluidized state conducive to the rapid disintegration of the brokencoke.

-Having set forth its objects and general nature, the invention will bebest understood from the following more detailed description of specicembodiments read with reference to the drawing.

Referring now to Figure 1 of the drawing, the system illustrated thereinessentially comprises a fluid-type coker 5, a centrifugal-type separatoror cyclone 21, and solids reheater or burner 30. The functions andcoaction of these elements will be forthwith described using theproduction of highly aromatic oils by coking reduced crude as anexample. It will be understood, however, that this may be used in agenerally analogous manner for coking operations of different types.

In operation, a heavy residual oil such as bottoms from van atmosphericor vacuum crude still may be supplied at still temperature to line 1wherein the oil is mixed with hot ycarrier solids supplied from aconventional aerated standpipe 3 at a temperature of about l350l400 F.as will appear more clearly hereinafter. The carrier solids, which maybesupplied through line 3 at a rate of about 2-40 weights/wt. of residuum,are preferably spheroidal particles vof copper or brass having aparticle size of about 200-1000 microns diameter. The oil feed ispartially vaporized upon contact with the hot carrier solids and themixture of vapors, liquid oil and solids is passed to a lower portion ofcoker 5 through a suitable distributing device such as grid 7.Additional uidizing medium such as steam, hydrocarbon gases or vapors,etc. may be added via line 9 and, if desired, together with the feedthrough line 1. The temperature in coker 5 is preferably maintained atabout l2001250 F. suitable for coking. The solids in coker 5 aremaintained in the form of a dense turbulent mass M5 uidized by theupiiowng gases and vapors to resemble a boiling liquid having a definiteinterface L5 and an apparent density of about 80-150 lbs. per cu. ft.Linear superficial gas velocities within mass M5 of about 2-5 ft. persecond are suitable for this purpose. At' the conditions vspeciiiedtheoil feed is converted into high yields of naphthav and higher boilingrange products rich in aromatic constituents while about 'on `thecarrier particles.V

10-15 wt. per cent of coke based on feed is deposited Volatile cokingproducts are withdrawn overhead from lever L5 to be passed via line 11to conventional product recovery equipment (not shown), if desired afterseparation of entrained solids and/or coke in cyclone separator 13provided with solids return pipe 15.

Carrier solids coated with coke may be withdrawn from mass M5(substantially at the rate of solids supply through line 1) through aconventional standpipe 17 aerated and/or stripped through one or moretaps t. At least a major proportion of the solids in standpipe 17 isdischarged into line 19 wherein they are picked up and quenched to atemperature of about 800-850 F. by steam or any other relatively inertgas of suitably low temperature. A 'dilute suspension of solids-in-gasis formed in line 19 and passed to separation stage 21 which may havethe form of a conventional cyclone separator of relatively lowefficiency. As the result of the considerable temperature drop from thetemperature level of coker 5 to that of quench line 19, the carrierparticles undergo a contraction of greater magnitude than that of theircoke layers, thereby cracking vthe latter. The cracked-up coke isfurther disintegrated in cyclone 21 due to frictional forces, so thatmost of the coke may be removed through line 23 as entrainment inquenchy gas to be recovered therefrom in any suitable manner, forinstance by a filter, electrical percipitator or the like.

Carrier solids 'usually containing suicient coke to maintain the heatbalance of the process are withdrawn from separator 21 via standpipe 2Sor the like and passed to line 27 supplied with air. A dilute suspensionof solids in air is passed through grid or similar distributing device29 into a lower portion of burner 30 to form therein a uidized rnass Maohaving an interface L30 in a manner` similar to M5. Combustion in massM30 is'preferably so controlled that the carrier solids are heated toabout l3501400 F. and substantially all the carbon is consumed. Fluegases are removed via line 32, if desired, after separation of entrainedsolids in cyclone 34 provided with dip-pipe 36. Reheated carrier solidssubstantially free of coke are returned to line 1 through standpipe 3aerated and/ or stripped via taps t, as described above. If desired,separator 21 may be so operated that less coke than that required forheat generation is withdrawn through line 25. In this case, a suitableproportion of the cokecarrying solids in standpipe 17 may be passeddirectly via line 38 and air lines 40 and 27 to burner 30. Thetemperature differential between coker 5 and burner 30 is sucient tobreak up the coke layers whereby coke combustion is enhanced.

An operation in which expansion rather than contraction of the carriersolids is relied upon for coke separation is illustrated in Figure 2 ofthe drawing. This svstem, which comprises a fluid-type coker 205, atransfer line burner 220, and a separator 222 will be described inconnection with an essentially thermal coking of a crude residuum.However, other analogous applications may occur to those skilled in thisart.

Referring now in detail to Figure 2, the residual oil feed may becharged through line 201, admixed with hot carrier solids supplied fromstandpipe 203 and passed through grid 207 to Coker 205 wherein a uidizedmass M705 having a levelLzosl isv formed with the aid of uidizing gassupplied through line 209, substantially in the manner described withreference to analogous elements of Figure l. However. in the case of thesystem of Figure 2 a 20% Ni steel is preferablv used as the carriersolid which mav he supplied to line 201 at a temperature of aboutl250l350 F. to maintain mass Mons at-a coking temperature of about975-1025 F. Volatile coking products are recovered via line 211 afterpassage through cvclrme 213 provided with dio-pipe 215. similarly asdescribed with reference to Figure l.

Coke carrying solids withdrawn through aerated standpipe 217 aresuspended in air in line 218. The suspension formed may be passedupwardly throughl a transfer line burner 220 at a superficial linear gasvelocity of about 5-15 ft. per second conducive to hindered settling andhigh turbulence of solids at an apparent density of about 20-50 lbs. percu. ft. The temperature in burner 220 may be about l250-l350 F.providing a sufficient temperature differential kkover the cokertemperature to permit rapid crack-up of the coke deposited on the steelparticles.

At the conditions specitied, only about 1,40-1/3 of the coke formed incoker 205 is burned in burner 220 to supply the heat requirements of theprocess.

Flue gases containing entrained carrier solids and broken up excess cokedischarge into cyclone separator 222 in which further cokedisintegration to a line powder takes place. This line coke powder iscompletely entrained by the ue gas withdrawn through line 225 and may berecovered by filtering or by electrical precipitation. Carrier solidsfree of carbon may be returned via standpipe 203 substantially at thetemperature of burner 220 as described above.

While in the foregoing description reference has been made chiefly tofluid-type coking which is the preferred embodiment of the invention, itis noted that the invention has a more general applicability.Substantial advantages may be secured by using the carrier solids of theinvention in slurry type, moving bed, transfer line or suspensoid cokingsystem, and even in ixed bed operation, as will be understood by thoseskilled in the art. The invention may also be applied to other processesinvolving the deposition of coke, particularly to other catalytichydrocarbon conversions, in a generally analogous manner.

Other modifications within the spirit of the invention may appear tothose skilled in the art.

The foregoing description and exemplary operations have served toillustrate specic embodiments of the invention but are not intended tobe limiting in scope.

What is claimed is:

1. The process of coking heavy residual oils in the presence ofsubdivided solids, which comprises contacting heavy residual oil at acoking temperature in a coking zone with a dense, turbulent, lluidizedmass of small metallic carrier solids having a thermal coeicient ofexpansion at least twice that of coke, whereby said oil is cracked and acoke layer is deposited on said solids, recovering volatile crackingproducts from said coking zone, passing coked carrier solids to athermal treating zone, subjecting said coked carrier solids in saidtreating zone to a change in temperature of sucient magnitude to cause asubstantial change in the particle size of said carrier solids as theresult of said high thermal expansion coeicient, whereby said coke layeris cracked to form coke fragments, separating said solids from saidfragmented coke, recovering coke so separated, reheating said carriersolids by combustion of the residue of the coke formed in said processto a temperature exceeding said coking temperature and returning saidreheated carrier solids to said coking zone.

2. The process of claim 1 in which said solids are selected from thegroup consisting of copper and brass.

3. The process of claim 1 in which said solids comprise nickel steel.

4. The process of claim l in which said temperature change is atemperature reduction of about 50-300 F.

5. The process of claim 1 in which said temperature change is atemperature increase of about 50-300 F.

6. The process of claim 1 n which said solids have a particle size ofabout 200-1000 microns.

The process of coking heavy residual oils in the presence of subdividedsolids, which comprises contacting heavy residual oil at a cokingtemperature in a coking zone with a dense, turbulent, iiudized mass ofsmall spheroidal metallic carrier solids having a thermal coeicent ofexpansion at least three times that of coke, whereby said oil is crackedand a coke layer is deposited on said solids, recovering volatilecracking products from said coking zone, separately withdrawing cokedcarrier solids from said coking zone, cooling said withdrawn carriersolids to a temperature about 50-300 F. below said coking temperature,whereby said layer is cracked to form coke fragments, subjecting saidsolids and coke fragments in a separation zone to a centrifugal motionto separate carrier solids from coke, recovering separated coke fromsaid separation zone, passing separated carrier solids from saidseparation zone to a heating zone, burning coke produced in said processin said reheating zone in contact with said carrier solids to reheat thelatter to a temperature higher than said coking temperature, andreturning carrier solids so reheated to said coking zone substantiallyat said higher temperature.

8. The process of claim 7 in which said coking temperature is about12001250 F. and said carrier solids are selected from the groupconsisting of copper and brass.

9. The process of claim 7 in which at least a portion of said carbonburned in said heating zone is supplied from said separation zone.

10. The process of coking heavy residual oils in the presence ofsubdivided solids, which comprises contacting heavy residual oil at acoking temperature in a coking zone with a dense, turbulent, iiuidizedmass of nely divided spheroidal metallic carrier solids having a thermalcoei-lcient of expansion at least three times that of coke, whereby saidoil is cracked and a coke layer is deposited on said solids, recoveringvolatile cracking products from said coking Zone, separately withdrawingcoked carrier solids from said coking zone, subjecting said withdrawncarrier solids to a limited combustion in a heating zone to raise thetemperature of said solids about 50-300 F. above said cokingtemperature, whereby said layer is cracked to form coke fragments andpart of said fragmented coke is burned, passing a mixture of carriersolids and unburned coke to a separation zone, subjecting said mixtureto centrifugal motion in said separation zone to separate coke fromcarrier solids, recovering coke from said separation zone, and passingseparated carrier solids from said separation zone to said coking zonesubstantially at said raised temperature.

l1. The process of claim 10 in which said carrier solids are suspendedin said combustion zone in a combustionsupporting gas to form arelatively dense, turbulent, uidized mass, liue gases being withdrawnfrom said combustion zone together with said mixture.

The process of claim 10 in which said carrier solids have a catalyticdesulfurization activity.

References Cited in the file of this patent UNITED STATES PATENTS

1. THE PROCESS OF COKING HEAVY RESIDUAL OILS IN THE PRESENCE OFSUBDIVIDED SOLIDS, WHICH COMPRISES CONTACTING HEAVY RESIDUAL OIL AT ACOKING TEMPERATURE IN A COKING ZONE WITH A DENSE, TURBULENT, FLUIDIZEDMASS OF SMALL METALLIC CARRIER SOLIDS HAVING A THERMAL COEFFICIENT OFEXPANSION AT LEAST TWICE THAT OF COKE, WHEREBY SAID OIL IS CRACKED AND ACOKE LAYER IS DEPOSITED ON SAID SOLIDS, RECOVERING VOLATILE CRACKINGPRODUCTS FROM SAID COKING ZONE, PASSING COKED CARRIER SOLIDS TO ATHERMAL TREATING ZONE, SUBJECTING SAID COKED CARRIER SOLIDS IN SAIDTREATING ZONE TO A CHANGE IN TEMPERATURE OF SUFFICIENT MAGNITUDE TOCAUSE A SUBSTANTIAL CHANGE IN THE PARTICLE SIZE OF SAID CARRIER SOLIDSAS THE RESULT OF SAID HIGH THERMAL EXPANSION COEFFICIENT, WHEREBY SAIDCOKE LAYER IS CRACKED TO FORM COKE FRAGMENTS, SEPARATING SAID SOLIDSFROM SAID FRAGMENTED COKE, RECOVERING COKE SO SEPARATED, REHEATING SAIDCARRIER SOLIDS BY COMBUSTION OF THE RESIDUE OF THE COKE FORMED IN SAIDPROCESS TO A TEMPERATURE EXCEEDING SAID COKING TEMPERATURE AND RETURNINGSAID REHEATING CARRIER SOLIDS TO SAID COKING ZONE.